Low-density dynamite



Patented Jan. 11, 3927.

JOHN MARSHALL, OF SWABTHEIOBE, PENNSYLVANIA. ASSIGNOR TO E. I. DU POINTDE NEMOUBS & COMPANY, OF WARE.

No Drawing. Application filed. July 30,

This invention relates to the manufacture of explosives having a liquidsensitizing a ent, and in particular to the manufacture o ammoniumnitrate explosives of the permissible type.

In the mining of coal, it is at times important to obtain the maximumpossible proportion, of lump product. For. thep'roduction of this typeof product, it has become recognized that for economy in operation,

the strongest possible explosive mustbe used,

having at the same time the lowest possible velocity, and a density suchas to give the proper distribution of explosive in the bore hole. Withthese properties must of course be coupled permissibility for use incoal mines, and sufiicient sensitiveness to detonation to. insurepropagation of explosion throughout a single charge.

In the development of this type of explos'ive, the disclosures ofWoodbury (U. S. P. 1,113,275 and 1,124,679) brought about a eat stepforward. By his method, the veil city of detonation is lowered byincreasing the size of the granules of the nitrate 0 ammonia, thereduction in velocity being in general proportional to the increase inthe size of the granules. This method of control of velocity has haddefinite limitations in that the use of a too coarsely granulatednitrate of ammonia will tend to interfere with thefstrength of theexplosive, and with the known absorbents it has been difiicult to obtainany material reduction in density (with consequent reduction invelocity) beyond certain rather definite limits without interferingseriously with the sensi- -tiveness of the dynamite.

Explosives of the type described above have previously been made of sucha density that a 1% x 8" cartridge has weighed 160 to 180 grams. (126 to142' sticks per lbs.), and have in general been made with ammoniumnitrate of such fineness that the major portion of the grains pass a 10mesh, and are held on a 60 mesh screen. Ammonium nireferred to as arelatively coarse ammonium WILMINGTON, DELAWARE, A CORPORATION OFDELA-LOW-DENSITY DYNAMITE.

1924. Scrial- No. 729,083.

nitrate. An example of such a composition follows:

' Per cent. Nitroglycerine 10 Ammonium nitrate 80 Wood flour ,5 Cornmeal5 Many variations haveof course been made in formulas of this type, asfor example, the substitution of 320% sodium chloride fora correspondingproportion of the ammonium nitrate; the use of similar proportions ofsodium nitrate in place of the ammonium nitrate; the substitution ofother carbonaceous materials, such as starch, ivory nut meal, sawdust,wood pulp, for the wood flour andcornmeal; and the use of otherexplosive liquids as substitutes for all or part of the nitroglycerine;as well as various changes in the relative proportions of the severalingredients mentioned.

Using previously known materials, the lowest density it has beenpossible to obtain in explosives of the ammonia permissible typecorresponds to a weight of about 135 gms. for 1 x 8" cartridges, andwhen using relativel coarse ammonium nitrate such as is described above,the lowest density it has been previously to obtain corresponds to aweight of about 151 gms. (150 sticks per 50 lbs.) in 1 x 8" cartridges,and this can be obtained only by the greatest care in the preparationand selection of materials. W

The explosives .manufactured from this type of coarse ammonium nitratehave in general had velocities below 2500 m/sec. In order to obtainlower densities than this, it has been necessary to use finer nitrate ofammonia, which in turn has caused an unclesirable increase in velocity.

I have discovered that by the use of a new absorbent material to replaceall or part of the carbonaceous materials previously used, I can obtainmaterial reduction in the density of the resulting dynamite, withoutinterfering to any serious extent with the ex plosive properties of thedynamite, and accompanied by an additional reduction in velocity overthat normally obtained by the use of the coarse ammonium nitrate, duedirectly to the reduction in densit obtained.

My new absorbent is obtained by the proper preparation of the stalk ofcorn, with which are included as equivalents the several varieties ofzea'mays, and of andropoga, or the non-saccharine sorghums.

I may, for example, prepare the new absorbent by the following method:The cornstalks, preferably well dried in advance, may-be stripped oftheir leaves and disintegrated by rasping, for .example, against ametallic wheel containing relatively small teeth on its periphery. .Thefinely divided material thus obtained may be passed over a screen, forexample one containing 10 meshes per linear inch. The screened mate;rial is then dried, when it is ready for use.

' For particular purposes it may be desirableto use different sizescreens for theabove, and it may also be found advisable at times towash the material before drying.

The product thus obtained is a finely divided material havin a distinctcellular structure, with very 1stinctive appearance when viewed under.the microscope. en the dry material is pressed in a layer about twoinches deep with a 25 lb. per square inch.

absorbent, though it is to be understood that the formulas here givenconstitute only a small proportion of the possible formulas in whlch thematerial can be used.

Per cent.

Nitroglycerine 10 Relatively coarse ammonium nitrate 75 Sodium nitrate 5Ground cornstalk 3 6 Wood flour 7 4 The decrease in density obtained inthe finished dynamite will of course vary with the extent to which thesubstitution of the new absorbent is carried. I have been able with suchformulas to obtain average densities corresponding to as low a weight as125 grams (181 sticks per case) for an 1 x8" cartridge without seriouslyaffecting the sensitivenessof the explosive. Considerably lowerdensities than this can be obtained by increasing the content ofcornstalk absorbent beyond the amount used in the above formulas. Thischange however must usually be accompanied by slight increases innitroglycerine content in order that sensitiveness may be maintained,and this in turn will in certain cases necessitate the inclusion ofadditional safety ingredients, for example N aCl or NH Cl, replacing forexample part of the ammonium nitrate.

The most important ranges in composition {vhich are possible may beindicated as folows Percent. N itroglycerine 7-15 Relatively coarseammonium nitrate 40-85 Sodium nitrate 0-20 Sodium chloride 0-20 Groundcornstalk 3-15 It is understood that there may be substituted otherliquid explosive materials for part or all of the nitroglycerine; forexample, tetranitrodiglycerine or ethylene glycol dinitrate that theremay be used any of the well recognized methods for depressing the flametemperature in order to obtain an explosive permissible for use in coalmines, and that there may be used ground cornstalk either alone or inconjunction with other carbonaceous materials without departing from theinvention.

I claim:

1. A low density dynamite comprising relatively coarse ammonium nitrate,ground cornstalk, and a liquid explosive ingredient, having a densitysuch that an 1 4 x 8 cartridge will weigh less than 146 grams, andhaving a velocity less than 2500 m/sec.

2. A low density dynamite comprising 50 to per 'cent of relativelycoarse ammonium nitrate, ground cornstalk, and a liquid explosiveingredient, and having a density such that an 1%x8" cartridge will weighless than 146 grams.

3. A low velocity dynamite comprising 50 to 80% relatively coarseammonium nitrate, ground cornstalk and 7 to 15% of a liquid explosiveingredient, and having a density such that an 1% x 8" cartridge willweigh less than 146 grams.

4. A low velocity dynamite of the ermissible type comprising 50 to 80%re atively coarse ammonium nitrate, a li uid explosive ingredient and 3to 10% of ely divided cellulosic material having the cellular structureof cornstalk and a density of less than 0.130, the density of saiddynamite being such that a cartridge 1 /;"x8" weighs as low as 130grams.

5. A low velocity dynamite of the permissible type comprising 40 torelatively coarse ammonium nitrate, a liquid explosive in redient, from1 to 20% of a salt of hydrochloric acid and an alkali, and from 3 to 15%of finely divided cellulosic material sity such that a 1%"X8" cartridgewill 1 having the cellular structure of cornstalk Weigh less than 130grams. and a density of less than 0.130, the density 7 A dynamitecomprising ammonium iiiof said dynamite being such that 'an trate,ground cornstalk and a liquid explo- 6 1%x8". cartridge Weighs as low as125 sive ingredient, said dynamite having a grams. density such that a1%x8 cartridge will 15 6.. A dynamite comprising ammonium ni- Weigh lessthan 146 grams. I

trate, ground cornstalk and a liquid explo- In testimony whereof I afiixmy signature. sive ingredient, said dynamite having a den- JOHNMARSHALL.

Certificate of Correction.

Patent No. 1,614,447, granted January 11, 1927 to JOHN MARSHALL.-.

It is hereb certified that error appears in the printed specification ofthe-shove mentioned pli tent requiring correction as follows: Page 1,hne 77, after the word previously insert the word possible, and that thesaid Letters Patent should he read. with this correction therein thatthe same may conform to the record of the -ase i the Patent Oifice.

L Sigiied and sealed this 1st day of March, A. ,D. 1927.

[ ML J. MQORE,

' Acting Oo Imissimaer of Palms.

